Fix PageGetExactFreeSpace() so that it actually behaves sensibly

tglsfdc · tglsfdc · commit 082aca9ec285 · 2008-02-10T20:39:08.000Z
if pd_lower &gt; pd_upper, rather than merely claiming to.  This would
only matter if the page header were corrupt, which shouldn't occur,
but ...
diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.77 2008/01/01 19:45:52 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.78 2008/02/10 20:39:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -489,6 +489,9 @@ PageGetExactFreeSpace(Page page)
 	space = (int) ((PageHeader) page)->pd_upper -
 		(int) ((PageHeader) page)->pd_lower;
 
+	if (space < 0)
+		return 0;
+
 	return (Size) space;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`*`
`9`	`9`	`*`
`10`	`10`	`* IDENTIFICATION`
`11`		`- * $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.77 2008/01/01 19:45:52 momjian Exp $`
	`11`	`+ * $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.78 2008/02/10 20:39:08 tgl Exp $`
`12`	`12`	`*`
`13`	`13`	`*-------------------------------------------------------------------------`
`14`	`14`	`*/`
`@@ -489,6 +489,9 @@ PageGetExactFreeSpace(Page page)`
`489`	`489`	`space = (int) ((PageHeader) page)->pd_upper -`
`490`	`490`	`(int) ((PageHeader) page)->pd_lower;`
`491`	`491`
	`492`	`+ if (space < 0)`
	`493`	`+ return 0;`
	`494`	`+`
`492`	`495`	`return (Size) space;`
`493`	`496`	`}`
`494`	`497`